1. Field of Invention
The present invention relates to an electronic device driving method, an electronic device, a semiconductor integrated circuit, and an electronic apparatus.
2. Description of Related Art
The related art includes active-matrix picture display apparatuses which, by using low-temperature polysilicon thin-film transistors (hereinafter “LT-TFTs”), a silicon integrated circuit, or organic transistors, drives electroluminescence elements (hereinafter “organic EL elements” and are irrespective of difference between emission material types) in which light is emitted by the flow of a driving current in an emission thin film, such as an organic semiconductor, vacuum fluorescent display devices (hereinafter “VFDs”), inorganic electroluminescence elements, laser devices, such as light-emitting-diodes (LED-device) surface-emitting lasers (VCSELs), or current-controlled thin-film emitting devices, such as field emission devices (FEDs). Driving control by TFT is suitable for a case in which a current of several μA (microamperes) or less causes thin-film light-emitting devices to emit light.
With noticeable progress in technological development, the emission efficiency of an organic EL element increases, and in accordance therewith, a small driving current enables light emission, so that each of the organic EL elements using LT-TFTs to form pixels becomes able to be driven by each LT-TFT.
However, with a rapid increase in the emission efficiency of the organic EL element, when a screen having uniform brightness is formed, accurate control becomes difficult because a driving current in a low gray scale region is too minute, even though no problem occurs based on a relatively large driving current in high and intermediate gray scale regions. The minute current in the region is 10 nA (nanoamperes), and is not so different from a leak current in the off mode of a driving transistor.
Accordingly, when a TFT to drive a light-emitting pixel is turned off, a leak current from an adjacent wire flows into a light-emitting pixel in a non-light-emitting state, so that a non-light-emitting device that cannot emit light emits weak light, thus causing contrast decreases and contour blurring. Under such circumstances, displaying must be performed in high and intermediate current ranges because accurate gray scale displaying cannot be performed in a minute current range, even if the emission efficiency of the organic EL element increases. This is a problem in reducing power consumption of an organic EL display in which power to cause organic EL elements to emit light is dominant.
To perform low-brightness displaying or displaying in the low gray scale region, LT-TFT circuits to drive pixels must accurately operate corresponding to gray scale currents. However, in accordance therewith, even if minute currents are written from a driver to LT-TFT circuits including analog memories of pixels, slow response in time of the LT-TFTs and leak current cause cases in which the writing does not end within the predetermined writing time required for a periodic display-refresh operation and in which it is difficult to accurately maintain the written values.